JPH06349411A - Method for sealing-off cathode-ray tube - Google Patents

Abstract

PURPOSE:To improve the yield of seal-off, and to simplify the structure of a seal-off jig, and to prolong the life time of a seal-off jig, and to simplify the maintenance of the seal-off. CONSTITUTION:A cylindrical heating element 14 is arranged in the periphery of a chip tube 5T of a CRT(cathode-ray tube), and a high frequency induction heating coil 15 is arranged in the periphery of the heating element 14. High frequency current is flowed to the high frequency induction heating coil 15, and the chip tube 5T is heated by the heat generation of the heating element 14 to seal-off the CRT.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for sealing off a cathode ray tube (CRT).

[0002]

2. Description of the Related Art A conventional CRT exhaust system will be described with reference to FIG. Box 1 with casters 2 attached to the bottom
Explosion-proof cage 3 is installed at the top of the
5 is stored and supported by the CRT holder 4.

A glass tip tube 5 extending from the lower end of the neck 5N of the CRT 5 is exchangeably connected to an oil rotary pump 11 and an oil diffusion pump 7, and the oil rotary pump 11 causes 10 ^-2 to 10 ^-3 Torr. And the oil diffusion pump 7 evacuates so as to achieve the degree of vacuum of 10 ⁻⁶ to 10 ⁻⁷ Torr. The seal-off jig 6 is attached in the middle of the tip tube 5T. Transformer 1 through brush 9
100V commercial power supply is connected to 0, and this is the transformer 10
The voltage is reduced to about 10 V by the voltage applied to the heater of the seal-off jig, and a current of about 10 A is applied to the heater. The oil diffusion pump 7 is water-cooled by the cooling water pump 12.
The vacuum degree measuring element 8 measures the degree of vacuum in the CRT 5.

Next, a conventional seal-off jig will be described with reference to FIG. A spiral heater 13 is arranged in a cylindrical heater cover HC made of metal via a two-layer plate-shaped mica MC for insulation, and the heater 13 is arranged around the tip tube 5T. The heater 13 is a ribbon-shaped resistance wire made of an alloy of 71% Fe, 23% Cr, and 6% Al, which is called a Kanthal wire. And this heater 1
An AC voltage of 10 V from the transformer 10 of FIG. 2 is applied between the heater 3 and the heater cover HC to flow a current of about 10 A. When this Kanthal wire is energized, it has a property that an oxide film is formed on the surface due to the heat generation of itself and becomes an insulating coating. However, since the reliability of insulation cannot be guaranteed with this oxide film, in practice, a heat-resistant insulator is applied to the heater 13 obtained by spirally forming a kanthal wire and used.

The seal-off steps (1), (2) and (3) of the tip tube 5T will be described with reference to FIGS. 4, 5 and 6. FIG. 4 shows a state in which a current is not yet applied to the heater 13. When the heater 13 is energized in FIG. 5, the tip tube 5T is softened by the heat of the heater 13 and the inside of the CRT 5 is evacuated to a high vacuum, so that the tip tube 5T is constricted by external air pressure. Deform. Then, as shown in FIG. 6, the tip tube 5T is finally sealed off.
After that, the lower portion of the seal portion of the tip tube 5T is cut as shown by the dotted line. The current flowing through the heater 13 is small at the beginning, and gradually increases after preheating, and gradually decreases in the latter half.

[0006]

The conventional CRT seal-off method has the following drawbacks. Since the structure is such that a spiral heater arranged around the tip tube causes an electric current to flow to generate heat, it is difficult to heat the tip tube uniformly, and it is difficult to stabilize the seal shape of the tip tube. Yield of tube seal-off is poor. The seal-off jig has a structure in which a spiral heater is arranged in the heater cover through a plate-shaped mica, which makes the structure complicated. The heater made of Kanthal wire is expensive and 3
Since the service life is only about a month, maintenance and replacement of the heater have to be frequently performed, and the work is complicated. In particular,
Replacing the heaters of hundreds of exhaust device seal-off jigs every three months is a difficult task. The insulation of the heater is weak to humidity. Assembly of the seal-off jig is complicated and requires fine adjustment before use. In order to heat the tip tube efficiently and uniformly, the heater must be close to the tip tube, so the heater comes into contact with the tip tube,
The heater itself or the tip tube may be damaged.

In view of the above point, the present invention has a good seal-off yield and a simple seal-off jig structure.
The present invention intends to propose a seal-off method for a CRT in which the seal-off jig has a long life and the maintenance of the seal-off is easy.

[0008]

According to the present invention, a cylindrical heating element 14 is arranged around a tip tube 5T of a CRT (cathode ray tube) 5, and a high frequency induction heating coil 15 is arranged around the heating element 14. Then, a high-frequency current is passed through the high-frequency induction heating coil 15 to heat the chip tube 5T by the heat generated by the heating element 14 to seal off the chip tube 5T.

[0009]

According to the present invention, a high frequency current is passed through the high frequency induction heating coil 15, whereby an eddy current flows through the heating element 14 to generate heat, which causes the CRT 5 in the exhaust gas.
The tip tube 5T is heated and sealed off.

[0010]

Embodiments of the present invention will be described in detail below with reference to FIG. As the exhaust device, the same exhaust device as the conventional example shown in FIG. 2 is used. As shown in FIG. 1, CRT5
The cylindrical heating element 14 is arranged around the cylindrical glass tip tube 5T, the cylindrical spiral coil 15 for high frequency induction heating is arranged around the heating element 14, and the high frequency induction heating coil 15 is arranged. A high-frequency current with a frequency of about 20 kHz to 200 kHz is applied to the heating element 14 to cause an eddy current, which causes the heating element 14 to generate heat and heat the tip tube 5T to seal off. The heating coil 15 is formed by spirally winding a wire material having a coating 15b on a copper wire 15a.

The heating element 14 is heat-resistant (800 °
A high resistance material that is resistant to oxidation (withstands temperatures of C to 900 ° C.), such as wrought cast iron meehanite is used. Other materials for the heating element 14 include CV-5 and Al.
-Cu alloy, ampoco 15, stainless steel, various iron, etc. are possible. The distance between the heating element 14 and the tip tube 5T is, for example, about 1 mm.

The current flowing through the heating coil 15 is small at first, and gradually increases when residual heat is generated, and gradually decreases in the latter half. As a result, the middle of the tip tube 5T is constricted by softening due to heating and external pressure, and finally sealed off. After that, unnecessary portions of the tip tube 5T are cut.

Conventionally, a high-frequency induction heating coil is arranged around the neck of the CRT, and during the exhaust of the CRT, the heating coil is energized to cause each electrode of the electron gun to generate heat, whereby each electrode is heated. A so-called gun bombarding process is performed to release the contained gas, but the heating coil is extended or moved to the melt of the heating element 14, and the heating coil simultaneously The heating element 14 may also generate heat. This simplifies the device for sealing off.

[0014]

According to the present invention described above, a cylindrical heating element is arranged around a tip tube of a CRT, a high frequency induction heating coil is arranged around the heating element, and the high frequency induction heating coil is arranged. A high-frequency current is applied to the tip to heat the tip tube by the heat generated by the heating element to seal off the tip tube, so the tip tube is uniformly heated by the heating element, resulting in good seal-off yield and seal-off. The structure of the jig is simple, the seal-off jig has a long life,
Maintenance of the seal-off jig (replacement of heating elements, etc.) becomes easy.

Further, according to the present invention, since the heating element can be heated by approaching the tip tube, the power consumption of the heating coil can be reduced. Further, even if the length of the heating element is shortened, the heating of the tip tube is easy, so the length of the tip tube after the seal-off can be shortened as much as possible, and the tip surface can be cut from the tube surface to the neck like Trinitron (registered trademark). It is suitable to be applied to a CRT having a long length to the end.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a seal-off jig according to an embodiment of the present invention.

FIG. 2 is a layout view showing a CRT exhaust device.

FIG. 3 is a sectional view showing a conventional seal-off jig.

FIG. 4 is a sectional view showing a seal-off step (1).

FIG. 5 is a sectional view showing a seal-off step (2).

FIG. 6 is a sectional view showing a seal-off step (3).

[Explanation of symbols]

 5 CRT 5N neck 5T chip tube 6 seal-off jig 14 heating element 15 coil for high frequency induction heating

Claims (1)

[Claims] 1. A cylindrical heating element is arranged around a tip tube of a cathode ray tube, a high frequency induction heating coil is arranged around the heating element, and a high frequency current is passed through the high frequency induction heating coil. A method of sealing off a cathode ray tube, characterized in that the tip tube is heated and sealed off by the heat generated by the heating element.